Resum:

Pea is a legume crop with worldwide economic importance that has been largely grownas a source of protein for animal and human nutrition for many centuries. However,yields of pea are usually reduced by biotic and abiotic stresses. Fusarium wilt causedby Fusarium oxysporum f.sp. pisi (Fop) is one of the most destructive disease of thiscrop. The use of resistant cultivars is widely recognized as the safest, most economicaland most effective method for controlling this disease. However, the constant evolutionof the pathogen drives the necessity to broaden the genetic basis of resistanceto Fop. Successful screening for disease resistance is based on (i) the availability oflarge and diverse germplasm collections, including wild relatives; (ii) the availability ofprecise and accurate screening techniques and genetic structure; (iii) the knowledge ofplant and pathogen biology, variability and host–pathogen interaction. In the presentwork, we aimed to identify and characterize new sources of resistance to Fop within aPisum spp. collection using different approaches and further understand mechanismsinvolved in resistance to this pathogen. To establish a standard, easy and usefulmethodology to evaluate the resistance of legumes to Fusarium oxysporum, apreliminary study evaluating the physiological and susceptibility response to thedisease of two contrasting genotypes of model plant Medicago truncatula has beenperformed. For this we evaluated the effect of several cultural conditions known toaffect the disease incidence such as plant age at inoculation, growth substrate and themethod of inoculation. The results obtained indicated that the method of inoculationstrongly affected fusarium wilt disease development while it was not significantlyaltered by the plant age or the inorganic growth substrate tested. This also allowed usto establish an optimum method of inoculation to study legume resistance to F.oxysporum that we then used to screen a Pisum spp. germplasm collection against oneisolate of Fop race 2. This showed a large variation in the disease response amongpea accessions ranging from highly resistant to susceptible, indicating the quantitativeexpression of the resistance. The repetition of the inoculation experiments on a subsetof 19 accessions, indicated that the established method of inoculation and evaluationwas robust and reproducible and confirmed the highly resistant phenotypes of 11accessions. We then aimed the characterization of the mechanism of resistanceresponsible for the resistance in these pea accessions. First, we collected the rootexudates of 12 pea accessions presenting differential responses to Fop race 2 todetermine their effect on Fop growth. While the root exudates of most pea accessionsstimulated Fop germination, some accessions did not and even inhibited Fopgermination. This indicated that some pea accessions express some constitutive prepenetrationmechanisms that might contribute to decrease or delay the building of...